Webform is a module that aids in making various one-off forms such as contact forms, surveys, order forms, reservations, CRM requests, and more.
To install the module, download the module and add it to your sites/all/modules directory. Enable it under /admin/build/modules.
You will now have a new node type called "Webform". From there, you simply need to create a new webform, add a title, description, confirmation message and other fields you may require. You can set up email settings to send an email upon form submission.
Finally, you can add several components (think fields). There are several component types available: fieldset, pagebreaks, grid, textarea, textfield, select (checkboxes, pulldown lists), email addresses and more.
The checkboxes under the "E-mail" header should be checked for each field you want to be included in the email that is sent when the form is submitted. This checkbox does not have to do with validating that field as an email address; that is handled by choosing "email" in the "Type" column.